I would suggest looking into some of Neal Godfrey's books (not sure on the spelling of her name). She has written numerous books on teaching children responsibility with money. Think one may be called "Money Doesn't Grow on Trees" or something like that. Also "A Penny Saved, A Penny Earned" or something like that... Sorry I am not better with exact info. Do a little search on amazon and see what you find.
At our house, you do chores because you are a member of the family. No one pays me to grocery shop, make dinner, do laundry, feed the cat, etc. Dh doesn't get money for mowing the lawn. We all do what needs to be done to keep the house running, not to earn money. We also do not pay for grades. I would rather put the emphasis on the pride they feel when doing well in that area.
Our 6 year old get $4.50 a week allowance. $2 of that is mad money to spend any way she wants. $2 goes into her savings account at the bank for long term savings - something big down the road - a car when she is 16, college, ?, stuff like that. 50 cents goes into the charity box and when it is full she gets to choose where she wants to donate it.
At first, she wasted that $2 every week - junky toy at the grocery store or stickers or whatever (I also did not allow completely free choice - she couldn't buy stuff with her allowance that she was not allowed to have anyway - like pop - we don't allow her to have that, with our money or hers. But she quickly learned that if she wasted (I mean spent!) that $ on something little, that when she saw a book or toy or something else, she had to start from scratch to save up for that. She now saves all the time. Once she saw a toy that was $99. Don't think she even remembers what it was anymore but she has saved up $40 for it!
I give allowance so she'll learn how to spend money wisely, not as a reward for chores or grades or behavior. This learning happens quickest and will "stick" better if I keep my big mouth shut and let her make poor choices, learn, and then make better choices. I second the "Parenting with Love and Logic" book!!!!